Boron-resistant Alternaria alternata (OG14) mitigates boron stress by improving physiological and antioxidative response in wheat (Triticum aestivum L.).

Effect of Alternaria alternata (OG14) isolated from a rock lichen (Xanthoria sp.) was investigated on the relief of boron stress in wheat. To determine the tolerance level to B stress, the fungus was grown at increasing boric acid (BA) concentrations in the range of 0.0-2.5 M. No significant change in colony development of the fungus was observed up to 1 M BA application compared to the control but after this dose, it decreased depending on the increase in the BA dose. When the element content of wheat seedlings was evaluated by ICP-MS, BA application increased B content together with Mg, P, K, Fe contents of the seedlings to very high levels compared to the control. However, fungus + BA treatments decreased the content of B and the other elements in the seedlings. The BA applications resulted in an increase in the levels of reactive oxygen species, including H2O2 and O2.-as well as lipid peroxidation in the seedlings. However, when the fungal inoculation was performed under the same BA conditions, the levels of these parameters decreased. The fungus inoculation stimulated the activity of all studied enzymes compared to BA applications. BA applications alone increased non - enyzmatic the oxidized ascorbate level more than the reducing ascorbate, leading to a decrease in the AsA/DHA ratio. The results show that A. alternata treatment can mitigate the negative effects of B stress on wheat seedlings by reducing ROS, LPO, B content, increasing the capacity of enzymatic and non-enzymatic antioxidants, and improving root and shoot length.

Psychrotolerant bacteria isolated from the leaf apoplast of cold-adapted wild plants improve the cold resistance of bean (Phaseolus vulgaris L.) under low temperature.

We have isolated psychrotolerant bacteria from the leaf apoplast of cold-adapted wild plants and aimed to investigate their effect on the cold resistance of bean (Phaseolus vulgaris L.). Based on the findings of 16S rRNA gene sequence analysis, 20 isolates belonging to 5 bacteria species (Pseudomonas fragi, P. chloropaphis, P. fluorescens, P. proteolytica and Brevibacterium frigoritolerans) were identified in the leaf apoplastic fluid of Draba nemorosa, Galanthus gracilis, Colchicum speciousum, Scilla siberica, Erodium cicutarium, respectively. We have determined that 6 of the 20 isolates have exhibited ACC (1-aminocyclopropane-1-carboxylate) deaminase activity and secreted different extracellular proteins under cold condition (+4 °C) compared to normal growth condition (28 °C). The six isolates were then inoculated independently of each other to the leaves of 10-day-old bean seedlings growing under normal conditions (25/22 °C, 16/8 h photoperiod), and the inoculated and uninoculated (control) seedlings were transferred to cold (9/5 °C, 16/8 h photoperiod) for 3 days. The bacterial inoculations have decreased freezing injury, ice nucleating activity and lipid peroxidation content in parallel with the decrease of reactive oxygen species level such as O2.- and H2O2 in the inoculated seedlings compared to the control. In addition, the inoculations of the isolates have stimulated the activity of apoplastic antioxidant enzymes including superoxide dismutase, catalase, peroxidase, and glutathione reductase. The results show that the inoculations improve the cold resistance of bean seedlings and the psychrotolerant bacterial isolates can be evaluated within the group of plant growth promoting bacteria (PGPB) which can increase tolerance of cold-sensitive crops.

Toxic effects of boron on growth and antioxidant system parameters of maize (Zea mays L.) roots.

The aim of this study was to investigate the possible oxidative stress and the antioxidant response, which were caused on maize by boron (B). For this, 11- and 15-day-old maize seedlings were subjected to 2 or 4 mM B in the form of boric acid (H3BO3) for 2 and/or 6 days. At the end of the treatment period, root length, hydrogen peroxide (H2O2) content, malondialdehyde (MDA) content and the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were measured. The results revealed that root length of plants, activity of antioxidative enzymes such as SOD, POX and CAT and also H2O2 contents and MDA levels were seriously affected by excess B. These results suggested that the oxidative stress occurred due to the toxic effect of B.